30 May 2022 to 2 June 2022
Asia/Dubai timezone

Effect of the connectivity of alluvial aquifers on groundwater flow and solute transport

31 May 2022, 11:45
15m
Oral Presentation (MS08) Mixing, dispersion and reaction processes across scales in heterogeneous and fractured media MS08

Speaker

anthony beaudoin (Université de Poitiers)

Description

The assumption that the heterogeneity of aquifers can be described with multilog-Gaussian distributions has been widely used (Law, 1944). However, the multilog-Gaussian assumption is inappropriate in alluvial aquifers (Zinn and Harvey, 2003). Alluvial aquifers, such as fluvial sediments containing paleochannels, present structures composed of interconnected bodies (Tidwell and Wilson, 1999). Alluvial aquifers can be described with binary distributions (Zinn and Harvey, 2003). Many authors have argued that the connectivity of alluvial aquifers is more important than the values of permeability K (Zappa et al., 2006). The connectivity of alluvial aquifers induces a channeling leading to significant increase in average flow rates and even more significant reduction of contaminant first arrival times (Molinari et al., 2019). Few works have performed three-dimensional detailed numerical simulations of groundwater flow and solute transport in binary distributions. In 2017, Jankovic et al. choose to study the effective permeability, the plume mean velocity, the BTC and the mass flux in multiLog-Gaussian, connected and disconnected K-fields introduced by Zinn and Harvey in 2003 (Jankovic et al., 2017). The bulk of the BTC was predicted quite accurately by the solution of the advection dispersion equation based on the first order approximation. In this work, the asymptotic value of the longitudinal dispersivity l is numerically estimated in three-dimensional multiLog-Gaussian, connected, intermediate and disconnected, K-fields from Monte Carlo parallel numerical simulations in advection – diffusion cases with a Peclet number Pe = <u> lc / dm = 100 where <u> is the mean flow velocity, lc is the correlation length of K-fields and dm is the diffusion coefficient. The following figure shows that the evolution of l with respect to the deviation p-pc presents a mountainous form in all the tested cases. p and pc are the volume fraction of low conductivity zones and the percolation threshold, respectively. The maximum value of l is obtained just after the percolation threshold pc. A detailed analysis will be performed by comparing the numerical results with the first order approximation and the percolation theory (Sahimi et al., 1986 ; Rubin, 1995).

References

Law JA. Statistical approach to the interstitial heterogeneity of sand reservoirs. Trans Am Inst Mech Eng 1944;155:202–22.
Zinn, B., and C. F. Harvey, When good statistical models of aquifer heterogeneity go bad: A comparison of flow, dispersion, and mass transfer in connected and multivariate Gaussian hydraulic conductivity fields, Water Resour. Res., 39(3), 1051, doi:10.1029/2001WR001146, 2003.
Tidwell, V. C., and J. L. Wilson, Permeability upscaling measured on a block of Berea Sandstone: Results and interpretation, Math. Geol., 31(7), 749 – 769, 1999.
Zappa, G., Bersezio, R., Felletti, F., & Giudici, M. (2006). Modeling heterogeneity of gravel-sand, braided stream, alluvial aquifers at the facies scale. Journal of Hydrology, 325(1-4), 134-153.
Molinari, A., Guadagnini, L., Marcaccio, M., & Guadagnini, A. (2019). Geostatistical multimodel approach for the assessment of the spatial distribution of natural background concentrations in large-scale groundwater bodies. Water research, 149, 522-532.
Jankovic, I., Maghrebi, M., Fiori, A., Dagan, G., 2017. When good statistical models of aquifer heterogeneity go right: the impact of aquifer permeability structures on 3d flow and transport. Adv. Water Resour. http://dx.doi.org/10.1016/j.advwatres.2016. 10.024.Fiori et al., 2017
Rubin, Y. (1995). Flow and transport in bimodal heterogeneous formations. Water Resources Research, 31(10), 2461-2468.
Sahimi, M., Hughes, B. D., Scriven, L. E., & Davis, H. T. (1986). Dispersion in flow through porous media—I. One-phase flow. Chemical engineering science, 41(8), 2103-2122.

Participation Online
Country France
MDPI Energies Student Poster Award No, do not submit my presenation for the student posters award.
Time Block Preference Time Block B (14:00-17:00 CET)
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Primary authors

anthony beaudoin (Université de Poitiers) Dr Alejandro Boschan (Grupo de Medios Porosos, Facultad de Ingeniería, UBA) Mr ivan Colecchio (Grupo de Medios Porosos, Facultad de Ingeniería, UBA)

Presentation materials